ABSTRACT
Natural rubber (NR) presents a number of advantages over other types of rubber but has poor resistance to chemicals and aging. The incorporation of ethylene propylene diene monomer (EPDM) into the NR matrix may be able to address this issue. Mineral fillers, such as carbon black (CB) and silica are routinely incorporated into various elastomers owing to their low cost, enhanced processability, good functionality, and high resistance to chemicals and aging. Other fillers have been examined as potential alternatives to CB and silica. In this study, phlogopite was surface-modified using 10 phr of compatibilizers, such as aminopropyltriethoxysilane (A1S), aminoethylaminopropyltrimethoxysilane (A2S), or 3-glycidoxypropyltrimethoxysilane (ES), and mixed with NR/EPDM blends. The effects of untreated and surface-treated phlogopite on the mechanical properties of the rubber blend were then compared with those of common fillers (CB and silica) for rubbers. The incorporation of surface-modified phlogopite into NR/EPDM considerably enhanced various properties. The functionalization of the phlogopite surface using silane-based matters (amino- and epoxide-functionalized) led to excellent compatibility between the rubber matrix and phlogopite, thereby improving diverse properties of the elastomeric composites, with effects analogous to those of CB. The tensile strength and elongation at break of the phlogopite-embedded NR/EPDM composite were lower than those of the CB-incorporated NR/EPDM composite by 30% and 10%, respectively. Among the prepared samples, the ES-functionalized phlogopite showed the best compatibility with the rubber matrix, exhibiting a tensile strength and modulus of composites that were 35% and 18% higher, respectively, compared with those of the untreated phlogopite-incorporated NR/EPDM composite. The ES-functionalized phlogopite/NR/EPDM showed similar strength and higher modulus (by 18%) to the CB/NR/EPDM rubber composite, despite slightly lower elongation at break and toughness. The results of rebound resilience and compression set tests indicated that the elasticity of the surface-modified phlogopite/NR/EPDM rubber composite was higher than that of the silica- and CB-reinforced composites. These improvements could be attributed to enhancements in the physical and chemical interactions among the rubber matrix, stearic acid, and functionalized (compatibilized) phlogopite. Therefore, the functionalized phlogopite can be utilized in a wide range of applications for rubber compounding.
ABSTRACT
Rubber compounding with two or more components has been extensively employed to improve various properties. In particular, natural rubber (NR)/ethylene-propylene-diene monomer rubber (EPDM) blends have found use in tire and automotive parts. Diverse fillers have been applied to NR/EPDM blends to enhance their mechanical properties. In this study, a new class of mineral filler, phlogopite, was incorporated into an NR/EPDM blend to examine the mechanical, curing, elastic, and morphological properties of the resulting material. The combination of aminoethylaminopropyltrimethoxysilane (AEAPS) and stearic acid (SA) compatibilized the NR/EPDM/phlogopite composite, further improving various properties. The enhanced properties were compared with those of NR/EPDM/fillers composed of silica or carbon black (CB). Compared with the NR/EPDM/silica composite, the incompatibilized NR/EPDM/phlogopite composite without AEAPS exhibited poorer properties, but NR/EPDM/phlogopite compatibilized by AEAPS and SA showed improved properties. Most properties of the compatibilized NR/EPDM/phlogopite composite were similar to those of the NR/EPDM/CB composite, except for the lower abrasion resistance. The NR/EPDM/phlogopite/AEAPS rubber composite may potentially be used in various applications by replacing expensive fillers, such as CB.
ABSTRACT
OBJECTIVES: The purpose of this study was to examine the effect of using a titanium nitride (TiN)-coated vertical distractor on osseointegration after implantation. STUDY DESIGN: Four adult mongrel dogs, weighing 9-10 kg, were used in this study. The lower premolars were extracted, and vertical distraction was performed after 10 weeks using 8 distraction devices (left, 4 titanium; right, 4 nitrified). A 7-day latency period was allowed before distraction began. The distraction device was activated at a rate of 0.5 mm twice a day for 5 days. After completing distraction, the device was removed after a consolidation period of 6 weeks and 24 implants were installed. The dogs were killed after 4 or 8 weeks. Histologic examinations were performed. RESULTS: The implant success rate was 100% in all of the study groups. Direct bone contact was achieved, and there were no significant differences between the control and experimental groups in the implantation area. CONCLUSION: The results suggested that the nitrified distraction device does not negatively affect osseointegration in the vertical distraction osteogenesis; therefore, it has the advantageous potential to substitute for the conventional distractor.
Subject(s)
Coated Materials, Biocompatible , Dental Implantation, Endosseous , Osseointegration , Osteogenesis, Distraction/instrumentation , Titanium , Animals , Dental Implants , Dogs , Implants, Experimental , Oral Surgical Procedures, Preprosthetic/instrumentation , Vertical DimensionABSTRACT
Exposure to a sublethal concentration of cadmium (Cd; 50 microg L(-1)) resulted in significantly increased Cd concentrations in the gill and digestive gland of the Antarctic bivalve Laternula elliptica. Continuous accumulation of Cd in the two organs during the 14-day exposure period was associated with sequestration of Cd to both the soluble cytosolic and insoluble particulate cell fractions. However, the contribution of each cell fraction to Cd sequestration differed between the two organs; in the gill, a larger portion of Cd was associated with the insoluble fraction, while in the digestive gland, both the soluble and insoluble fractions sequestered similar amounts of Cd. Metal-binding components in the insoluble cell fraction were not identified in this study. On the other hand, a metallothionein-like protein (MTLP) was the major Cd-detoxifying component in the soluble cell fraction of the gill and digestive gland. The amount of MTLP increased linearly with exposure time and the amount of Cd accumulated in the tissue, which suggests a potential utility of MTLP as a biomarker for exposure to Cd and possibly other metals.
